Precision depth seed planter

ABSTRACT

A precision depth planter including a plurality of furrowforming units mounted on a main frame for relative vertical movement, each unit including a pair of depth gauge wheels for carrying the unit and for regulating the depth of the furrow formed thereby. A seed dispensing unit is mounted on the frame directly above each furrow-forming unit and includes a seed container and selecting mechanism for delivering seeds to the furrow, the several selecting mechanisms being commonly driven from a drive shaft extending transversely between the dispensing units. A separate hydraulic cylinder acts on each furrow-forming unit to maintain a constant force on said unit regardless of the position thereof relative to the main frame. A ground-engaging sensing unit mounted on the planter frame measures soil hardness and in conjunction with a hydraulic control valve acts to vary the force exerted by the hydraulic cylinders to maintain a uniform planting depth irrespective of variations in soil hardness.

. United States Patent [1 1 Cayton et a1.

11] 3,749,035 [451 July 31, 1973 PRECISION DEPTH SEED PLANTER [73]Assignee: Deere & Company, Moline, Ill. [22] Filed: Dec. 28, 1970 [21]Appl. No.: 101,916

[52] US. Cl Ill/85, 172/4, 172/413, 172/484, 111/62 [51] Int. Cl. A0lc5/00 [58] Field of Search 111/85-87, 62, 6; 172/4, 413, 484, 462, 487,239, 7, 9

Primary ExaminerRobert E. Pulfrey Assistant Examiner-Stephen C.Pellegrino Attorney-H. Vincent Harsha, Harold M. Knoth, William A.Murray and John M. Nolan [5 7] ABSTRACT A precision depth planterincluding a plurality of furrow-forming units mounted on a main framefor relative vertical movement, each unit including a pair of depthgauge wheels for carrying the unit and for regulating the depth of thefurrow formed thereby. A seed dispensing unit is mounted on the framedirectly above each furrow-forming unit and includes a seed containerand selecting mechanism for delivering seeds to the furrow, the severalselecting mechanisms being commonly driven from a drive shaft extendingtransversely between the dispensing units. A separate hydraulic cylinderacts on each furrow-forming unit to maintain a constant force on saidunit regardless of the position thereof relative to the main frame. Aground-engaging sensing unit mounted on the planter frame measures soilhardness and in conjunction with a hydraulic control valve acts to varythe force exerted by the hydraulic cylinders to maintain a uniformplanting depth irrespective of variations in soil hardness.

17 Claims, 7 Drawing Figures PATENIEI] JUL 3 1 I975 SHEET 1 UF 5INVENTORS DAVID W. CAYTON LESLIE W. JOHNSON PATENIEDJUL31 I973 SHEET 2BF 5 3 m T Y NA C w N D W A D LESLIE W. JOHNSON PATENIEUJULB 1 m5 3'.749 035 SHEET a BF 5 DAVID W. CAYTON LESLIE W. JOHNSON S R 0 m m m w 9!9N 11 com -1- Now NNN 3 mm; 0 2 F m q N mg 02 wow 1 mm 8 N9 n. N2 ma 05mm Q2 08 m M FAT 9N OON NON @9 r.

1 PRECISION DEPTH SEED PLANTER BACKGROUND OF THE INVENTION gated framesupporting a plurality of spaced, rear-- wardly extending, individualplanting units for independent vertical movement relative to the frame.Each unit includes a furrow opener, a press wheel mounted behind thefurrow opener which serves also as a depth gauge wheel, and a seedcontainer and dispensing mechanism mounted above the opener forintermittently depositing seeds in the furrow formed thereby. If it isdesired to apply pesticides to the soil simultaneously with the seedplanting operation, a pair of hoppers therefor are normally mounted onthe unit above the combination press and depth gauge wheel. A- springpressure mechanism is commonly provided between the frame and each unitfor exerting a downward force on the latter, the force exerted by thespring mechanism-being in addition to that provided by the weight ofthe'unit and the quantity of seed and pesticide contained. thereon. 1

Certain features of this conventional design contribute to a lack ofuniformity in planting depth. For example, since the press wheel, fromwhich the planting depth is gauged, is necessarily'mounted at somedistance behind the furrow opener, fore-and-aft variations in groundlevel along the planting row result in corresponding variations inplanting depth along the row. in addition to this inherent gaugingerror, a substantial variation in planting depth results from variationsin the down force acting on the unit, since for a constant soilhardness, such down force variations cause corresponding variations inthe depth of penetration of the unit gauge wheels, which, in turn,results in variations in planting depth. The down pressure acting on theunits is basically a function of two variables: first, the quantity andthus weight of the seed and pesticide contained in the respectivehoppers, this quantity continually depleting during the plantingoperation between refillings of the hoppers, and second, the height ofthe unit relative to the frame and thereby the force exerted by thespring in the down force mechanism, this force being inverselyproportional to the spring length. Thus, as the unit moves verticallyrelative to the frame to follow the surface of the ground, the plantingdepth of the unit varies inversely with its vertical position. inaddition to its effect on planting depth, such variations in downpressure on v the unit, because transmitted through the press. wheelthereof, result also in variations in the compaction of soil surroundingthe planted seed.

A still further'source of planting depth error is that caused byvariations in soil hardness, such variations commonly existing betweendifferent fields, between different areas within the same field, andbetween the sameareas in a field over a period of time. For aconstantdown force on the planting unit, the gauge wheels thereof willnaturally penetrate further in soft than in hard soil, resulting in adeeper planting depth in soft as opposed to hard soil.

Planting depth, and more broadly the entire seed environment, isbecoming an increasingly important concern of the farmer as every effortis made to increase crop yield. Fast and uniform seed germination, animportant factor in increasing crop yield, requires a uniform, optimumplanting depth.

SUMMARY or THE lNVENTlON It is, accordingly, an object of the presentinvention to provide a seed planter capable of precisely maintaining auniform planting depth. More specifically, it is an object of theinvention to provide a planter having a main frame supporting aplurality of trailing planting units, wherein variations in downpressure on the individual units resulting from variations in verticalheight of the unit relative to the main frame, and from variations inthe quantity of seed and pesticide contained thereon, are eliminated. Itis a further object to provide a planter having press wheel meanscapable of uniformly compacting the soil in the planting rows,irrespective of the down force acting on the planting unit. It is yet afurther object to provide a planter having a main frame and a pluralityof individual planting units, the planter including means for exerting auniform down force on each individual planting unit irrespective ofthe'vertical position thereof relative to the main frame, further toprovide means for selectively varying the down force so exerted on theunits, and still further to provide means for simultaneously anduniformly varying the down force acting on the several unitsflt is afurther object to provide such a planter having means for automaticallyvarying the down force on the several planting units in response to soilhardness.

These and other objects are achieved, according to the invention, by theprovision of a planter having a transversely extending main frame, aplurality of relatively light-weight furrow-forming units mounted on theframe for independent vertical movement, and an equal number ofassociated seed dispensing units, each of the latter units beingindependently mounted on the main frame and extending above itsassociated furrowforming unit in vertical spaced relation. Eachfurrowforming unit includes a furrow Opener means, a pair of adjustabledepth gauge wheels mounted on opposing sides of the opener means forregulating the running depth thereof, and a separate press wheel meansin following relation to the furrow opener and carried by a separatesubframe structure mounted for independent vertical movment relative tothe opener. Each overlying dispensing unit comprises a seed hopper andassociated seed selecting mechanism, the latter communicating with thefurrow formed by the furrow opener through a vertically extending seedconveying conduit, and a pair of pesticide hoppers and associateddispensing means mounted rearwardly of the seed hopper and alsoincluding a pair of vertically extending conduits for delivering thepesticide to the plant row. The seed selecting mechanism contained inthe several dispensing units is driven from a powered shaft extendingtransversely between the units, as are the several pesticide dispensingmeans associated therewith.

A positive down pressure is exerted on each of the relatively lightfurrow-forming units by means of a hydraulic actuator or cylinder actingbetween the unit and the planter main frame. The tractor hydraulicsystem supplies constant pressure fluid to the cylinder whereby theforce exerted'by the latter is essentially independent of its length.Consequently, the down force acting on the unit remains essentiallyuniform irrespective of its vertical position relative to the frame. Theoperation of this system is contrasted with that of the conventionalspring pressure mechanism, wherein the down force varies with verticalposition of the unit.

The hydraulic actuators on the several units are connected with eachother and with the tractor hydraulic system in a parallel arrangement,the latter system including a pressure control valve whereby the forceexerted on the units by the actuators can be varied uniformly andsimultaneously. This is to be contrasted with the conventional springpressure down force mechanism in which adjustments must be separatelymade to each unit, a time-consuming operation. The pressure controlvalve can be actuated either manually or automatically in response tosoil hardness. Although the adjustable depth gauge wheels on thefurrowforming units are effective to approximately regulate the runningdepth of the associated furrow opener means, variations in soil hardnesscreate corresponding variations in furrow depth for a constant downforce; the softer the soil, the deeper the gauge wheels penetrate thesurface of the ground, and thus the deeper the planting depth, andconversely, the harder the ground, the shallower the gauge wheelpenetration and planting depth. To maintain a constant, optimum plantingdepth throughout a field having relatively hard and soft areas, a lesserdown force must therefore be employed in the soft areas than in the hardareas.

The automatic soil hardness sensing unit of the invention comprises arelatively wide shoe mounted on the planter frame and adapted to ride onand follow the surface of the ground, a relatively narrow, weighted shoemounted on the wide shoe and adapted to penetrate the surface of theground at various depths corresponding to variations in ground hardness,and means for comparing the relative vertical positions of the two shoesand actuating the hydraulic pressure control valve on the tractor indirect response to variations in their positions. For example, inrelatively soft ground, the weighted, narrow shoe will ride at a deeperlevel with respect to the wide shoe than would be the case in harderground, and such deeper penetration is translated into a lesser downforce on the planting units, thereby maintaining a uniform furrow depththroughout both hard and soft areas.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred embodiment of theinvention will be described in conjunction with the accompanyingdrawings in which:

FIG. 1 is a perspective view of the planter taken from the left rear,with all but one of the planting units shown in outline form for thesake of clarity;

FIG. 2 is a perspective view from the left front, again with all but oneof the planting units in outline form;

FIG. 3 is a side elevation view of one of the planting units;

FIG. 4 is a view taken generally along the line 4-4 of FIG. 3;

FIG. .5 is a schematic representation of the hydraulic system of theinvention;

FIG. 6 is a side elevation view of the soil hardness sensing unit of theinvention, on a scale reduced from that of FIGS. 3 and 4; and,

FIG. 7 is a plan view of the sensing unit of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the ensuing description,rightand left-hand reference is determined by standing at the rear ofthe planter and facing the direction of travel.

Referring first to FIGS. 1 and 2 of the drawings, the planter comprises,generally, a transversely elongated, rectangular cross-sectional mainframe 10 having a plurality of individual planting units 12 mounted intrailing relation thereon. In the embodiment illustrated, the frame isprovided with a three-point or integral hitch structure 14 on its centerportion for attachment to a tractor, and a pair of verticallyadjustable, groundengaging wheel assemblies 16 and 18 on opposite sidesthereof to gauge the operating height of the main frame 10. As will beapparent to those skilled in the art, the principles of the presentinvention could as well be incorporated in a planter of the pull ortrail type, wherein the frame structure is provided with a fore-and-aftdraft member adapted for connection to the drawbar of a tractor.

The three-point hitch structure 14 of the illustrated embodimentincludes a pair of left and right brackets 20 and 22 secured to theframe 10 at equal distances to the left and right, respectively, of thelongitudinal centerline thereof, the left bracket 20 consisting of upperand lower members 24 and 26 held to the respective surfaces of themember 10 by means of elongated bolts 28, and the right bracket 22consisting of upper and lower members 30 and 32 similarly held to themember 10. The opposite ends of a transverse bar 34 are rigidly clampedbetween the upper and lower, forwardly extending portions of thebrackets 20 and 22. Left and right pairs of forwardly extending members40 and 42 are rigidly fixed, as by welding, to the respective ends ofthe bar 34 inwardly of the brackets 20 and 22, and support a pair ofleft and right transversely aligned hitch pins 44 and 46 between theirforward ends for receiving the two outer or lower arms of the tractorintegral hitch mechanism. The hitch device 14 further includes a centerbracket 48 comprising a left and right pair of upstanding, triangularmembers 50 and 52 rigidly secured to the upper surface of the framemember 10, and a lower pair of left and right members 56 and 58 securedto the lower surface of the frame 10 directly below the respectivetriangular members 50 and 52. The middle portion of the bar 34 is heldbetween the forward ends of the lower members 56 and 58 and uppermembers 50 and 52 by means of bolts 62. A short transverse bar 66 isclamped to the upper ends of the triangular members 50 and 52 and has atransversely spaced pair of forwardly extending plates 68 and 70 fixedto its midportion. A hitch ball 72 is mounted between the lower forwardportion of the plates 68 and 70 to receive the center arm of the tractorintegral hitch and thereby complete the tractorplanter connection.

The gauge wheel assemblies 16 and 18 of the planter are essentiallymirror images of each other and comprise, generally, a forwardlyextending arm 74 pivotally mounted at 76 between a pair of left andright angle members 78 and 80, and having a stub axle 82 fixed to itsforward end and rotatably receiving a groundengaging wheel 84 thereon.An extensible and retractable jack 86 acts between a bracket 88 on theforward end of the arm 74 and the upper portion of a bracket 92 securedto the frame 10. The bracket 92 consists of left and right member 94 and96, respectively, which are secured to the upper surface of the framewith bolts 98, which bolts also hold the angle members 78 and 80 to theunderside of the member 10. It will be apparent that extension andretraction of the jack 86 is effective to pivot the arm 74 about the pin76 and thereby raise and lower the wheel 84 relative to the planterframe. In operation, the wheel assemblies 16 and 18 act as height gaugemeans for the planter main frame in the operating position, and supplyoperating power to the seed and pesticide dispensing mechanisms carriedby the planting units.

The latter function of the wheel assemblies 16 and 18 is accomplished inconjunction with the drive mechanism illustrated in FIG. 2. Themechanism is of more or less conventional design and comprises,generally, a sprocket 100 mounted on each of the wheels 84 for rotationtherewith, a transverse jackshaft 102 rotatably supported above the mainframe 10, and a pair of drive chains 104 drivingly connecting thesprockets 100 with a pair of aligned sprockets 106 on opposite ends ofthe shaft 102. To compensate for the different speeds of rotation of thewheels 84 as the planter is turned to the right or left, each of thesprockets 106 is coupled to the shaft 102 through a one-way clutch orratchet device 108. The jackshaft 102 is supported on the frame 10 by aplurality of transversely spaced upstanding brackets 110. Power istransmitted from the jackshaft 102 rearwardly to a transverse driveshaft extending between the several planting units 12 through a sprocket112 on the right side of the jackshaft 102, an aligned sprocket (notshown) on the planting unit drive shaft, and a drive chain 114 trainedaround the drive and driven sprockets.

Although the planter illustrated is provided with six planting units 12,it will be apparent from the ensuing description that this number may bereadily increased or decreased, since the units are constructed for easyaddition to or removal from the main frame 10. Each of the plantingunits 12 consists of a seed dispensing unit 116 mounted rigidly on themain frame 10 and extending rearwardly therefrom, and a furrow-formingunit 1 18 mounted for relative vertical movement on the main frame andextending rearwardly in underlying relation to the associated seeddispensing unit.

Upper and lower pairs of parallel links or levers 120 and 122 mount thefurrow-forming units on the main frame for vertical parallel movement,thereby enabling the unit to follow the surface of the ground whileremaining parallel thereto. The forward ends of the upper links 120 arepivoted at 124 on a pair of upper brackets 126 which, in turn, arerigidly secured to the main frame 10 and which, as will subsequentlyappear, form the main supporting structure for the seed dispensing unit116. The forward ends of the lower links 122 are likewise pivotedat 128to a pair of lower brackets 130, the latter lying directly beneath theupper brackets 126 and being secured thereto and to the main frame 10with fore-and-aft elongated bolts 132. An H-shaped supporting structure,comprising a pair of vertical legs or members 134 rigidly interconnectedby a transverse cross member 136, is pivotally carried at 138 and 140 bythe upperand lower links, respectively, and in turn carries thefurrow-forming means and press wheel subframe of the unit. Centered onthe back side of the cross member 136 are a pair of transversely spacedvertical plate members 142 which, in conjunction with transverseconnecting walls 144, 146, and 148, define a pair of fore-and-aft,downwardly converging passages and 152. As will subsequently bedescribed in greater detail, seed and pesticide from the respectiveselecting mechanisms on the overlying seed dispensing unit areintroduced into the top of the passages 150 and 152, respectively, dropdownwardly therethrough, and are deposited in the furrow formed by thefurrowforming means. The latter means, in the embodiment illustrated,comprises conventional furrow-opener runner blades 154 fixed to thelower edge of the plate members 142, though it will be readily apparentto those skilled in the art that various other conventional devices,such as a pair of rearwardly diverging disk blades, could be substitutedfor the runner blades 154. A pair of offset straps 156 extend betweenthe transverse ends of a bracket member 158, fixed centrally to theunderside of the cross member 136, and the forward end of the runner 154to support the latter relative to the H-shaped structure. Pivotallymounted on the same bracket 158 at 160 and extending downwardly andrearwardly therefrom are a pair of gauge wheel support arms 162. Atransverse axle 164 is fixed to the ends of the arms 162 and rotatablysupports a pair of gauge wheels 166 on its opposite ends, the verticalposition of the wheels being adjustable relative to that of the runner154 to regulate the approximate running depth of the latter. The wheels166 are maintained in various positions of adjustment by means of a pin168 selectively positionable in any of a plurality of elongated slots170 in the lower rear portions of the plate members 142. The portion ofthe'pin intermediate the plates 142 is received by a short bracket 174fixed to the midpoint on the axle 164 and extending forwardly betweenthe plates 142.

The furrow-forming unit 118 further includes a press wheel subframestructure, indicated generally by the numeral 176. The structure 176comprises a pair of fore-and-aft side members 178 pivoted at theirforward ends to the legs 134 of the H-shaped supporting structure, themembers 178 extending alongside and outwardly of the gauge wheels 166and being joined rearwardly thereof by a transverse tubular member 180.The rearward ends of the members 178 converge inwardly and receive apair of press wheels 182 therebetween on a transverse axle 184 which, inturn, is rotatably supported at its ends in aligned bearing members 186fixed to and projecting downwardly from the members 178. The verticalpivotal movement of the subframe 176 relative to the H-shaped supportingstructure is limited by means of a lost motion connecting link 188. Therear end of the link 188 is pivotally mounted on a pin 190 between apair of spaced plates 192 fixed to the transverse tube 180, while theforward end thereof extends between the plates 142 and is provided withan elongated aperture 194 for receiving a pin 196 extending transverselybetween the plates 142.

When disposed in its normal operating position, illustrated in FIGS. 1and 3, the pin 196 is centered in the aperture 194, thereby permittingapproxiamtely equal pivotal movement of the subframe both above andbelow its normal position.

A pair of conventional covering disks 198 are carried by the press wheelsubframe 176 between the depth gauge wheels 166 and the press wheels182. The disks are angled inwardly, the angle being adjustable as willpresently appear, to direct soil into the furrow and cover the seedtherein. A separate subframe mounts the disks 198 on the press wheelsubframe for adjustment of their vertical position, the subframecomprising a pair of fore-and-aft members 200 pivoted at 202 to the sidemembers of the subframe 176, and rigidly connected at their forward endswith a pair of longitudinally spaced cross members 204. An upstandingbracket 206 is fixed to the upper edges of the members 204 and extendsforwardly between the plates 192. The bracket 206 is provided with aplurality of apertures 208 for receiving a pin 210, the latter extendingbetween the plates 192 and being releasably retained therein. Each diskis rotatably mounted on the lower end of a vertical standard 212 which,in turn, is fixed to the bottom side of a lower mounting bracket 214.The lower bracket 214 and an identically-shaped upper bracket 216 areclamped to the cross members 204 with bolts 218, the structure describedpermitting ready adjustment of both the lateral position and angle ofthe disks 198.

A conventional diverging pesticide distributor 220 is mounted behind thepress wheels 182 on a U-shaped supporting structure 222, the legs of theU being secured to the rearward ends of the side members 178 of thepress wheel subframe 176. As will be described subsequently in moredetail, pesticide is supplied to an inlet opening 224 on the upperportion of the dispenser from a hopper on the seed dispensing unit.

As previously mentioned, the brackets 126 supporting the forward ends ofthe furrow-forming unit upper parallel links 120 also comprise the mainsupporting structure for the associated seed dispensing unit 116. Theremainder of the supporting structure includes a pair of fore-and-aftpesticide hopper supports 226, and a pair of inclined members 228rigidly connecting the rearward ends of the brackets 126 with theforward ends of the supports 226. A seed selecting mechanism 230 ofconventional design and an associated hopper 232 are mounted between thebrackets 126 on a pair of fore-and-aft, transversely extending bolts234. The selecting mechanism 230, which may, for example, be of theconventional seed plate type, is driven from a transverse shaft 236extending therethrough. A telescoping transverse shaft 238 (see FIG. 2)drivingly interconnects the shafts 236 on each adjacent pair of plantingunits 12, the resulting series of shafts 236 and 238 conjunctivelydefining a single transverse shaft extending between the extreme leftand right planting units 12 and comprising the common drive for all ofthe units. The planting unit drive shaft, as already described, isdriven from the jackshaft 102 through the chain 114. A telescoping seedconveying conduit 240 extends vertically between the discharge area 242of the selecting mechanism 230 and the upper opening of the seed passage150 on thefurrow-forming unit 118. The seed from the hopper 232 thusdrops through the tube 240 to the passage 150, thence through thepassage to the bottom of the furrow formed by the runner 154.

A pair of transversely spaced angle members 244 are interposed betweeneach side of the mechanism 230 and the adjacent brackets 126 and arerigidly held therein with bolts 234. The cylinder portion 246 of asingle-acting hydraulic actuator 248 is pivotally mounted between theforward ends of the members 244 on trunnions 250, and the rod portion252 thereof is pivotally connected at 254 with a transverse support 256extending between the lower parallel links 122.

The functions served by the actuator 248 will be de- I tailed below.

Mounted directly behind the seed hopper 232 is a matched pair ofpesticide hoppers 258 and 260, the forward hopper 258 being forinsecticide and the rear hopper 260 for herbicide. Each hopper 258 and260 includes a conventional rotary distributing mechanism 262 and 264,respectively, in its lower portion, the mechanisms being driven bysprockets 266 and 268, respectively. The sprockets 266 and 268 are inturn driven by a chain 270 from a sprocket 272 on the left end of theseed selecting mechanism drive shaft 236. An adjustable idler wheel 274maintains proper running tension in the chain 270. A telescopingpesticide conveying tube 276 extends between-the outlet opening 278 ofthe distributing mechanism 262 in the forward hopper 258 and the upperopening of the rear passage 152 defined by the vertical members 142 andtransverse connecting walls 146 and 148. The pesticide from the hopper258 thus passes through the tube 276 to the passage 152, thence throughthe passage 152 to the furrow formed by the runner 154. The upper andlowr ends of the tube 276 are pivotal about their respective mountingsto accommodate the change in angular relationship between the tube andits supports as the furrow-forming unit 118 moves vertically relative tothe overlying seed dispensing unit 116. In a similar manner, atelescoping tube 280 connects the outlet 282 on the rear pesticidehopper 260 with the inlet 224 on the diverging dispenser 220. Pesticidefrom the rear hopper thus passes downwardly through the tube 280, thencethrough the dispenser 220 which distributes it in an even band over thesurface of the plant row.

It will be apparent from the structure described thus far that thefurrow-forming unit 118 of the planter is relatively light in weight,this fact stemming primarily from the removal of the seed and pesticideselecting mechanisms and hoppers to the independently mounted seeddispensing unit 116. It will also be apparent that the weight or downforce on the unit 118 resulting from the weight thereof will remainconstant through the planting operation, irrespective of the quantity ofmaterial contained within the pesticide and seed hoppers. Although sucha constant down force would be desirable if operating in soil of aconstant hardness, since soil hardness quite often varies substantiallywithin a single field and from one field to another, it is desirable toinstead provide means exerting a down force on the unit which variesinversely with soil hardness. The desirability of such a varaible downforce arises from the fact that the force acting on the depth gaugewheels of the furrow-forming unit determines the depth below groundsurface at which they will ride, and this depth, in turn, directlydetermines the depth of the furrow formed by the furrow-forming means,and thus the depth at which the seed is planted.

According to the present invention, means for providing such a variabledown force on the furrowforming unit is provided in the form of thehydraulic actuator 248 acting between the planter frame and the unit.Referring to FIG. 5 of the drawings, the several hydraulic actuators 248on the planter are connected in a parallel arrangement with each other,through hydraulic lines or hoses 284, and with a conventional source ofhydraulic fluid on the tractor through line 286. The fluid source on thetractor includes a pressure control valve 288 which is actuatable bymeans of control lever 290 to vary the pressure of the fluid within theactuators 248 and thus the force exerted thereby on the furrow-formingunit.

Although it is contemplated that the valve 288 could be manuallycontrolled by the tractor operator, whereby the operator would visuallysense variations in soil hardness and actuate the valve accordinglywithout interrupting the planting operation, according to the presentinvention means in the form of a soil hardness sensing unit 292 isprovided to continually sense and automatically regulate the pressurecontrol'valve 288 in response to soil hardness. As shown schematicallyin FIG. 5, the sensing unit or ground feeler device 292 is mountedcentrally on the main frame member 10, between the two center plantingunits 12. Although the particular location of the unit is not critical,it is important that it operate in soil which has not been previouslycompacted by either the tractor wheels 294 or planter drive wheels 84.As illustrated in detail in FIGS. 6 and 7, the sensing unit 292 ismounted on the main frame 10 for relative vertical movement in a mannersimilar to the several furrow-forming units 118, with upper and lowerpairs of parallel links 296 and 298, re-

spectively. The forward ends of the links 296 and 298 are pivotallyattached to upper and lower pairs of mounting brackets 300 and 302which, in turn, are clamped to the main frame member 10 with fore-andaftelongated bolts 304, while the rearward ends thereof are pivotallyconnected to the opposite sides of an upright transverse channel member308. A relatively wide shoe or ground feeler 310 having an upwardlycurved leading edge is fixed to the lower edge of the channel 308 and isadapted to ride on and follow the surface of the ground. Due to itsrelatively large surface area and lightweight construction, the shoe 310will ride at essentially the same level in both hard and soft soils.Disposed adjacent to the left side of the shoe 310 and pivotallyconnected thereto is a second, relatively narrow shoe or ground feeler312 which is adpated also to ride on the surface of the ground. Thepivotal connection between the two shoes 310 and 312 is effected by atransverse pin 314 extending through the channel 308, and receiving abearing member 318 fixed to the narrow shoe 312. The extreme rearportion of the shoe 312 supports a weight 320 exerting a constantdownward force on the shoe. The combination of this force and therelatively narrow width of the shoe causes the shoe to penetrate thesurface of the soil, the depth of penetration being inverselyproportional to the relative hardness thereof. In a relatively softsoil, for example, the shoe will penetrate to a considerable depth,while in a relatively hard soil, the penetration will be relativelyslight.

Since as previously noted the wide shoe 310 is adapted to follow thesurface of the ground irrespective of its hardness, a comparison of therelative vertical positions of the shoes 310 and 312 will provide aquantitative measure of soil hardness. Means for comparing thesevertical positions, and actuating the pressure control valve 288 on thetractor in response to variations therein, is provided in the form of amaster-slave hydraulic system comprising a master cylinder 322 on thesensing unit 292 and a slave cylinder 324 on the tractor connected tothe cylinder 322 with a single hydraulic line 326. The cylinder. 322 ismounted on the channel member 308 of the sensing unit, and includes avertical push rod 328 coupled with the narrow shoe 312. The couplingcomprises a transverse pivot member 330 mounted on the shoe 312, a firstarm 332 fixed to the left end of the member 330 and pivotally connectedat its rearward end to the weight 320, and a second arm 334 fixed to theright end of the member 330 and pivotally connected at its forward endto the push rod 328 of the cylinder 322. In operation, vertical movementof the narrow shoe 312 relative to the wide shoe 310 is transmittedthrough the coupling mechanism 330, 332, and 334 to the push rod 328 ofthe cylinder 322. The resulting displacement of fluid in the cylinder322 results in corresponding movement of the push rod 336 of the slavecylinder 324, and thus movement of the control lever 290 of the pressurecontrol valve 288. The components of the system are so designed that theresulting change in pressure of the fluid in the lines 284 and 286 andplanting unit actuators 248 is of just the required mamtitude tomaintain a constant furrow depth. For example, as the planter passesfrom an area of relatively hard soil to an area of relatively soft soil,

the narrow shoe 312 of the sensing unit will assume adeeper runninglevel relative to the wide shoe 310. This downward movement of the shoe312 is transmitted to the push rod 328. As the push rod is movedupwardly into the cylinder 322, fluid is displaced therefrom into theline 326, an equal quantity of fluid is displaced from the other end ofthe line into the slave cylinder 324, and the push rod thereof isadvanced forwardly, thus moving the control lever 290 of the valve 288in a clockwise direction as viewed in FIG. 5. Such clockwise movement ofthe lever 290 in turn produces a lower fluid pressure in the fluidactuators 248 and thus a lesser down force acting on the furrow-formingunits 118. This reduction in down force is of sufficient magnitude tojust offset the tendency of the unit depth gauge wheels to sink into therelatively soft soil, and thereby maintains the unit at the samevertical position relative to the ground surface. in a similar thoughinverse manner, the pressure in the actuators 248 is increased as theplanter moves from a relatively soft area to a relatively hard area,thereby increasing the down force on the units 118 and elf-setting thetendency of the unit to ride at a higher level in the harder soil.

We claim:

1. A precision depth seed planter comprising: a main frame; a plantingunit mounted on the main frame and including a furrow-forming unitconnected to the frame for relative vertical movement, saidfurrow-forming unit including a ground penetrating furrow-forming means,and depth gauge means for supporting the unit relative to the ground andregulating the approximate operating depth of said furrow-forming means;hydraulic actuator means acting between said main frame and saidfurrow-forming unit for exerting a downward vertical force on said unitwhich is independent of the vertical position thereof relative to saidframe; a sensing unit mounted on the main frame for relative verticalmovement and including ground-engaging means for measuring groundhardness; and hydraulic control means operatively connecting saidhydraulic actuator means and said sensing unit for increasing anddecreasing the vertical force exerted by said actuator means on saidfurrow-forming unit in response to the sensing unit engaging harder andsofter ground, respectively.

2. The invention defined in claim 1 wherein said planting unit furtherincludes a seed dispensing unit mounted on said main frame above saidfurrowforming unit, said seed dispensing unit including a seed containerand selecting mechanism; and a seed conveying conduit extending betweensaid seed dispensing unit and said furrow-forming unit for conveyingseeds from said seed selecting mechanism to the furrow formed by saidfurrow-forming means.

3. The invention defined in claim 2 wherein said seed dispensing unit isdisposed in substantially fore-and-aft alignment with saidfurrow-forming unit, said seed selecting mechanism includes a downwardlydirected seed discharge opening disposed generally vertically from saidfurrow-forming means, and said seed conveying conduit extends generallyvertically between said seed discharge opening and said furrow-formingmeans.

4. The invention defined in claim 3 wherein said seed dispensing unit isrigidly connected to the main frame, said furrow-forming unit includesparallel linkage means mounting said unit on the main frame for parallelvertical movement, and said hydraulic actuator means acts between saidseed dispensing unit and said parallel linkage means.

5. The invention defined in claim 2 wherein said planting unit furtherincludes a press wheel unit pivotally mounted on and extendingrearwardly from said furrow-forming unit, said press wheel unitincluding press wheel means mounted rearwardly of and in substantiallyfore-and-aft alignment with said furrowforming means.

6. The invention defined in claim 2 including a plurality of saidplanting units mounted in transverse alignment on said main frame, eachunit including a seed dispensing unit and associated selectingmechanism; transverse drive shaft means extending between adjacent seeddispensing units; means on each of said dispensing units drivinglyconnecting said drive shaft means with the seed selecting mechanismcontained thereon; ground-engaging drive wheel means mounted on saidmain frame; and means drivingly connecting said ground-engaging drivewheel means with said drive shaft means for driving said seed selectingmechanisms.

7. The invention defined in claim 1 wherein said depth gauge meanscomprises a pair of wheels disposed on opposite sides of and insubstantially transverse alignment with said furrow-forming means.

8. The invention defined in claim 1 including a plurality offurrow-forming units connected to the frame for relative verticalmovement, and a plurality of hydraulic actuators acting between saidmain frame and said furrow-forming units for exerting a vertical forceon the furrow-forming units; and wherein said control means includesmeans for simultaneously and uniformly regulating the force exerted bysaid hydraulic actuators.

9. The invention defined in claim 8 wherein said control means includesa source of hydraulic fluid under pressure; means for regulating thepressure of said fluid; and fluid line means connecting said hydraulicactuator means in parallel with each other and with said source ofhydraulic fluid.

10. The planter defined in claim 1 wherein said sensing unit comprises apair of ground-engaging sensors, and means for comparing the relativevertical positions of said sensors.

11. The planter defined in claim 10 wherein one of said sensors isrelatively wide and is adapted to ride substantially on the surface ofthe ground, and the other of said sensors is relatively narrow and isadapted to penetrate the surface of the ground, the vertical distancebetween said wide and narrow sensors being greater in soft than in hardground.

12. The planter defined in claim 11 wherein said hydraulic control meansis operative to increase and decrease the vertical force exerted by saidactuator means on said furrow-forming unit in response to a decrease andincrease, respectively, in the vertical distance between said wide andnarrow sensors.

13. An agricultural implement comprising: a main frame; at least oneground-working unit mounted on said main frame for relative verticalmovement; ground-engaging depth gauge means on said groundworking unitsupporting said unit relative to the ground and regulating theapproximate operating depth thereof; hydaulic actuator means actingbetween said main frame and said ground-working unit for exerting avertical force on said unit which is independent of the verticalposition thereof relative to said main frame; a sensing unit mounted onthe main frame for relative vertical movement and includingground-engaging means for measuring ground hardness; and hydrauliccontrol means operatively connecting said actuator means and saidsensing unit for varying the force exerted by said actuator means inresponse to variations in ground hardness and thereby regulating theprecise operating depth of said ground-working unit.

14. In an agricultural implement having a main frame, at least oneground-engaging unit mounted on the main frame for relative verticalmovement, and hydraulic actuator means acting between said main frameand said unit for exerting a vertical force on the latter, meansresponsive to soil hardness to regulate the force exerted by saidactuator means and thereby maintain said ground-engaging unit at aconstant vertical position relative to the surface of the ground, saidmeans comprising: a first relatively wide sensor adapted to ride on andsubstantially level with the surface of the ground; a second, relativelynarrow sensor adapted to ride on the ground and penetrate the surfacethereof, the depth of penetration of said narrow sensor varying withsoil hardness; means operatively connecting said wide and narrow sensorsfor comparing the levels of said sensors and thereby measuring the depthof penetration of said narrow sensor; and hydraulic fluid supply meansfor supplying fluid under pressure to said hydraulic actuator means,said supply means including means responsive to and operative to varythe fluid pressure in relation to the depth of penetration of saidnarrow sensor, whereby said ground-engaging unit is maintained at aconstant vertical position relative to the surface of the groundirrespective of variatons in soil hardness.

15. A precision depth seed planter comprising: a main frame; afurrow-forming and closing structure including a furrow-forming bladeand associated gauge wheels regulating the operating depth of the blade,said structure being pivoted for vertical movement on the main frame; aplurality of tanks adapted to carry variable amounts of material andfeed material to said furrow opening and closing structure; meanssupporting all of said tanks on the main frame independently of saidfurrow-forming and closing structure; hydraulic actuator means actingbetween said main frame and said structure exerting a downward forcethereon; ground feeler means supported on the frame engageable with theground for measuring the hardness thereof; and control means operativelyconnected to said ground feeler means and said hydraulic actuator meansfor increasing and decreasing the downward pressure by said actuatormeans on said structure in response to the ground feeler means engagingharder and softer ground respectively.

16. The precision depth seed planter as set forth in claim 15 in whichsaid frame includes a rearward protween the structure and the rearwardend 'of the lever. i t i

1. A precision depth seed planter comprising: a main frame; a plantingunit mounted on the main frame and including a furrowforming unitconnected to the frame for relative vertical movement, saidfurrow-forming unit including a ground penetrating furrow-forming means,and depth gauge means for supporting the unit relative to the ground andregulating the approximate operating depth of said furrow-forming means;hydraulic actuator means acting between said main frame and saidfurrow-forming unit for exerting a downward vertical force on said unitwhich is independent of the vertical positioN thereof relative to saidframe; a sensing unit mounted on the main frame for relative verticalmovement and including ground-engaging means for measuring groundhardness; and hydraulic control means operatively connecting saidhydraulic actuator means and said sensing unit for increasing anddecreasing the vertical force exerted by said actuator means on saidfurrow-forming unit in response to the sensing unit engaging harder andsofter ground, respectively.
 2. The invention defined in claim 1 whereinsaid planting unit further includes a seed dispensing unit mounted onsaid main frame above said furrow-forming unit, said seed dispensingunit including a seed container and selecting mechanism; and a seedconveying conduit extending between said seed dispensing unit and saidfurrow-forming unit for conveying seeds from said seed selectingmechanism to the furrow formed by said furrow-forming means.
 3. Theinvention defined in claim 2 wherein said seed dispensing unit isdisposed in substantially fore-and-aft alignment with saidfurrow-forming unit, said seed selecting mechanism includes a downwardlydirected seed discharge opening disposed generally vertically from saidfurrow-forming means, and said seed conveying conduit extends generallyvertically between said seed discharge opening and said furrow-formingmeans.
 4. The invention defined in claim 3 wherein said seed dispensingunit is rigidly connected to the main frame, said furrow-forming unitincludes parallel linkage means mounting said unit on the main frame forparallel vertical movement, and said hydraulic actuator means actsbetween said seed dispensing unit and said parallel linkage means. 5.The invention defined in claim 2 wherein said planting unit furtherincludes a press wheel unit pivotally mounted on and extendingrearwardly from said furrow-forming unit, said press wheel unitincluding press wheel means mounted rearwardly of and in substantiallyfore-and-aft alignment with said furrow-forming means.
 6. The inventiondefined in claim 2 including a plurality of said planting units mountedin transverse alignment on said main frame, each unit including a seeddispensing unit and associated selecting mechanism; transverse driveshaft means extending between adjacent seed dispensing units; means oneach of said dispensing units drivingly connecting said drive shaftmeans with the seed selecting mechanism contained thereon;ground-engaging drive wheel means mounted on said main frame; and meansdrivingly connecting said ground-engaging drive wheel means with saiddrive shaft means for driving said seed selecting mechanisms.
 7. Theinvention defined in claim 1 wherein said depth gauge means comprises apair of wheels disposed on opposite sides of and in substantiallytransverse alignment with said furrow-forming means.
 8. The inventiondefined in claim 1 including a plurality of furrow-forming unitsconnected to the frame for relative vertical movement, and a pluralityof hydraulic actuators acting between said main frame and saidfurrow-forming units for exerting a vertical force on the furrow-formingunits; and wherein said control means includes means for simultaneouslyand uniformly regulating the force exerted by said hydraulic actuators.9. The invention defined in claim 8 wherein said control means includesa source of hydraulic fluid under pressure; means for regulating thepressure of said fluid; and fluid line means connecting said hydraulicactuator means in parallel with each other and with said source ofhydraulic fluid.
 10. The planter defined in claim 1 wherein said sensingunit comprises a pair of ground-engaging sensors, and means forcomparing the relative vertical positions of said sensors.
 11. Theplanter defined in claim 10 wherein one of said sensors is relativelywide and is adapted to ride substantially on the surface of the ground,and the other of said sensors is relatively narrow and is adapted topenetrate the surface of the ground, the vertical distanCe between saidwide and narrow sensors being greater in soft than in hard ground. 12.The planter defined in claim 11 wherein said hydraulic control means isoperative to increase and decrease the vertical force exerted by saidactuator means on said furrow-forming unit in response to a decrease andincrease, respectively, in the vertical distance between said wide andnarrow sensors.
 13. An agricultural implement comprising: a main frame;at least one ground-working unit mounted on said main frame for relativevertical movement; ground-engaging depth gauge means on saidground-working unit supporting said unit relative to the ground andregulating the approximate operating depth thereof; hydaulic actuatormeans acting between said main frame and said ground-working unit forexerting a vertical force on said unit which is independent of thevertical position thereof relative to said main frame; a sensing unitmounted on the main frame for relative vertical movement and includingground-engaging means for measuring ground hardness; and hydrauliccontrol means operatively connecting said actuator means and saidsensing unit for varying the force exerted by said actuator means inresponse to variations in ground hardness and thereby regulating theprecise operating depth of said ground-working unit.
 14. In anagricultural implement having a main frame, at least one ground-engagingunit mounted on the main frame for relative vertical movement, andhydraulic actuator means acting between said main frame and said unitfor exerting a vertical force on the latter, means responsive to soilhardness to regulate the force exerted by said actuator means andthereby maintain said ground-engaging unit at a constant verticalposition relative to the surface of the ground, said means comprising: afirst relatively wide sensor adapted to ride on and substantially levelwith the surface of the ground; a second, relatively narrow sensoradapted to ride on the ground and penetrate the surface thereof, thedepth of penetration of said narrow sensor varying with soil hardness;means operatively connecting said wide and narrow sensors for comparingthe levels of said sensors and thereby measuring the depth ofpenetration of said narrow sensor; and hydraulic fluid supply means forsupplying fluid under pressure to said hydraulic actuator means, saidsupply means including means responsive to and operative to vary thefluid pressure in relation to the depth of penetration of said narrowsensor, whereby said ground-engaging unit is maintained at a constantvertical position relative to the surface of the ground irrespective ofvariatons in soil hardness.
 15. A precision depth seed plantercomprising: a main frame; a furrow-forming and closing structureincluding a furrow-forming blade and associated gauge wheels regulatingthe operating depth of the blade, said structure being pivoted forvertical movement on the main frame; a plurality of tanks adapted tocarry variable amounts of material and feed material to said furrowopening and closing structure; means supporting all of said tanks on themain frame independently of said furrow-forming and closing structure;hydraulic actuator means acting between said main frame and saidstructure exerting a downward force thereon; ground feeler meanssupported on the frame engageable with the ground for measuring thehardness thereof; and control means operatively connected to said groundfeeler means and said hydraulic actuator means for increasing anddecreasing the downward pressure by said actuator means on saidstructure in response to the ground feeler means engaging harder andsofter ground respectively.
 16. The precision depth seed planter as setforth in claim 15 in which said frame includes a rearward projectingportion overlying the furrow opening and closing structure, saidstructure is supported for vertical movement on the frame by afore-and-aft extending lever pivoted at its forward end on the frame andat its rearward end to the strUcture; and said actuator means extendsbetween the frame and lever.
 17. The precision depth seed planter as setforth in claim 16 in which the furrow-forming blade and gauge wheels areclosely adjacent the pivotal connection between the structure and therearward end of the lever.